An organic light-emitting device includes a thin film which contains a light-emitting organic compound and which is arranged between an anode and a cathode, and is driven by applying a voltage between the electrodes to inject holes and electrons. The holes and the electrons recombine in the device to excite the light-emitting organic compound. Light emitted when the light-emitting organic compound returns from the excited state to the ground state is used.
There have been recent significant advances in organic light-emitting devices. Organic light-emitting devices have high luminance at low applied voltages, various emission wavelengths, and rapid response and are thin and lightweight. This suggests the possibility that they are used in a wide variety of applications.
However, in the case where the application of organic light-emitting devices to, for example, full-color displays is contemplated, current devices have insufficient stability from a practical standpoint. In particular, blue-light-emitting devices have a problem of a reduction in luminous efficiency with time during a continuous operation. It is necessary to overcome the problem.
The reduction in luminous efficiency may be caused by the deterioration of a light-emitting layer via an excited state, i.e., a gradual deterioration of the light-emitting layer due to the repeated excitation and relaxation. Hereinafter, the deterioration is referred to as “deterioration via an excited state”. In PTL 1, in order to reduce an excited triplet state of a light-emitting layer material that may be highly associated with the deterioration via an excited state, a triplet-state quencher is incorporated together with the light-emitting layer material, thereby preventing the deterioration.